Transmissible spongiform encephalopathies (TSEs) are a group of fatal neurodegenerative disorders affecting humans and animals. Although rare, the recent outbreak of Bovine Spongiform Encephalopathy(BSE) in cattle and Chronic Wasting disease (CWD) in cervids and the transmission of the disease from cattle to humans have caused great concern. This problem is aggravated by the lack of an efficient, sensitive and early diagnosis as well as many uncertainties surrounding the unprecedented nature of the infectious agent, its mechanism of propagation and the species-barrier that controls prion transmission. The major goals of this Program Project are to understand the mechanism of transmission and pathogenesis of BSE and CWD prions, to estimate the risk of these infectious agents to propagate disease to other animals and especially to humans, to assess the mechanisms and routes of prion dissemination among animals and to develop novel strategies for ante-mortem detection of infected animals. A team of accomplished scientists with widely recognized expertise and track record of contributions in this field will work collaboratively to reach these goals. Project 1 (Juergen Richt, PL) proposes to study in detail mutant and knock out cows and assess the role of genetic forms of BSE in disease transmission, susceptibility and species barrier. For these studies, we plan to generate and characterize knock in transgenic cattle expressing a PrP mutation recently identified in a natural BSE case in USA. We will also use transgenic mice models expressing wild type and mutant bovine PrP and in vitro studies of PrP replication using the PMCA. Project 2 (Glenn Telling, PL) proposes to generate and use transgenic mice models to assess the strength of various species barriers and the influence of prion strains. We will study the susceptibility of various models to be infected by CWD as well as the possibility that deer models may be infected by prions from other species. To address this aim, experiments will be done in transgenic mice models and using in vitro conversion studies. Project 3 (Claudio Soto, PL) proposes to study the replication of CWD and BSE prions in vitro, evaluate tissue distributions of infectious protein, enlighten the routes of transmission and develop a diagnostic assay. For this purpose, we will use the PMCA technology, recently developed in Dr Soto's lab to mimic the prion replication process. The Administration Core (core A) (Claudio Soto, Director) will facilitate and integrate Projects and Cores and take care of all administrative aspects needed for the smooth operation of the Program. The Tissue Core (core B) (Pierluigi Gambetti, Director) will process, analyze and store the tissue samples generated and provide access to the members to a biosafety facility to manipulate BSE infectious material. The findings generated in this Program will have undoubtedly contribute to understand the pathogenesis, route of propagation and early detection of these two worrisome zoonotic prion diseases.